1. Field of the Invention
The invention relates to a process for treating dyed velvet fabrics to achieve two-toned, lustrous effects.
2. Description of Related Art
Mercerization is a well known technique for treating natural cellulosic fibers, e.g. cotton or rayon fibers, in order to enhance the luster, strength and feel of the fiber. In accordance with this process, the yarn or fabric is immersed in a 20-30% by weight aqueous solution of alkali hydroxide maintained at a temperature normally below 200.degree. F., usually 50.degree.-90.degree. F. until the fibers swell and become plastic. After removal from the alkali solution, the resulting alkali cellulose fibers are tentered to avoid shrinkage and washed with hot water, optionally containing a neutralizing acid, to progressively remove the alkali. Progressive replacement of alkali with water leads to the development of stable Cellulose II or cellulose hydrate I fiber. The resulting fibers or fabrics are then dried. In instances where the fibers or fabrics are to be dyed, the dying normally takes place after mercerization. This general process was first described by John Mercer in U.S. Pat. No. 8,303, issued Aug. 19, 1851.
Variations of the mercerization process are also disclosed in U.S. Pat. Nos. 1,058,459, 2,142,043, and 2,769,685.
U.S. Pat. No. 665,680 discloses a process for preparing cellulose-based textile yarns of enhanced luster comprising immersing the yarn in an alkaline solution containing a colloid such as starch, either before or after dying the yarn.
In another process disclosed in U.S. Pat. No. 2,524,113, rayon textile fabrics are first treated with an aqueous solution containing a water soluble reaction product of formaldehyde, lactic acid, ethanol and urea, followed by treatment with an aqueous caustic solution which stabilizes the treated fabric. Two-tone dye effects may be achieved by applying the caustic only in a pattern, e.g. stripes or designed patterns, followed by dying. The pattern area treated with caustic exhibits a greater affinity for dyestuffs than the non-treated area, thereby leading to two-tone effects.
Two-toned effects in woven fabrics such as velvets, which comprise a woven backing containing short pile fibers, may be achieved by using pre-dyed yarn fibers of different colors for the backing and the pile yarns, but this adds considerably to the expense of apparel manufacture. Another technique for obtaining colored velvets is to employ yarns of different chemical composition for the backing and pile fibers in the construction of an undyed velvet composite, and then dye the composite using a dye which has an affinity for dying only the backing fibers, or using a dye bath containing two chemically different dyes, one of which has a greater affinity for dying the pile fibers and the other of which has a greater affinity for dying the backing fibers. However, these techniques produce two-toned fabrics of either excessive color contrast or of very poor color contrast as between the pile and backing fibers.